5. Conclusion and perspective
The application of graphite as cathode in rechargeable batteries, particularly in DIBs and AIBs, gained significant attention during the last few years. This perspective outlined the study of structure, mechanism of anion intercalated compound. Then, recent advance in various graphite cathode for the application in AIBs and DIBs are discussed. The discussion in this review has illustrated that significant amount of researches are devoted into enriching the anion intercalation devices. DIBs and AIBs using graphitic materials as cathodes are promising energy storage devices ascribed to their relatively high energy density and low cost. Although considerable progress have been achieved, future research is still necessary to deal with the following challenges: (1) Relatively lower CE. DIBs and AIBs deliver a low CE especially under lower rate and at the beginning several cycles. This is partly because the intercalation voltage is out of the stable voltage window of electrolyte from cathode, and partially resulted from the unstable SEI formed at the anode when using high specific capacity and low reaction potential alloying type anode, i.e. Al, Sn etc. The low CE from the anode should be solved flowing LIB solutions through electrode modification (nano sizing or nano composition) and electrolyte additive (get stable SEI). However, the modification of the graphitic cathode and the exploration of suitable electrolyte is a tremendous task, which requires deep thought and painstaking exploration. (2) The specific capacity of the cathode materials are relatively low, less than 124 mAh g-1 , which is hard to satisfy the energy density required. Further increase of the cathode specific capacity is an oncoming task.
